asp.net-core - api 不活动后，asp.net 核心托管服务休眠

Question

我有一个托管服务，每分钟检查一个电子邮件帐户。我还将 MVC 与 Web API 2.1 一起使用。为了让我的托管服务启动，我必须通过调用 API 方法来“唤醒它”。在 Web API 一段时间不活动后，托管服务进入休眠状态并停止检查电子邮件。就像它正在收集垃圾一样。如何让它连续运行？

协助将不胜感激。

启动.cs:

public void ConfigureServices(IServiceCollection services)
    {
        services.AddSwaggerGen(c =>
            {
                c.SwaggerDoc("v1", new Info {Title = "CAS API", Version = "v1"});

                // Set the comments path for the Swagger JSON and UI.
                var xmlFile = $"{Assembly.GetEntryAssembly().GetName().Name}.xml";
                var xmlPath = Path.Combine(AppContext.BaseDirectory, xmlFile);
                c.IncludeXmlComments(xmlPath);
            })

            .AddCors(options =>
            {
                options.AddPolicy("CorsPolicy",
                    builder => builder.WithOrigins(Configuration["uiOrigin"])
                        .AllowAnyMethod()
                        .AllowAnyHeader()
                        .AllowCredentials());
            })
            .AddHostedService<EmailReceiverHostedService>()
            .Configure<EmailSettings>(Configuration.GetSection("IncomingMailSettings"))
            .AddSingleton<IEmailProcessor, MailKitProcessor>()
            .AddSingleton<IEmailRepository, EmailRepository>()


          ...

EmailReceiverHostedService.cs:

using CasEmailProcessor.Options;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using System;
using System.Threading;
using System.Threading.Tasks;

public class EmailReceiverHostedService : IHostedService, IDisposable
{
    private readonly ILogger _logger;
    private readonly Timer _timer;
    private readonly IEmailProcessor _processor;
    private readonly EmailSettings _emailConfig;


    public EmailReceiverHostedService(ILoggerFactory loggerFactory,
        IOptions<EmailSettings> settings,
        IEmailProcessor emailProcessor)
    {
        _logger = loggerFactory.CreateLogger("EmailReceiverHostedService");
        _processor = emailProcessor;
        _emailConfig = settings.Value;
        _timer = new Timer(DoWork, null, Timeout.Infinite, Timeout.Infinite);
    }

    public Task StartAsync(CancellationToken cancellationToken)
    {
        _logger.LogInformation("Timed Background Service is starting.");
        StartTimer();
        return Task.CompletedTask;
    }

    public Task StopAsync(CancellationToken cancellationToken)
    {
        _logger.LogInformation("Timed Background Service is stopping.");
        StopTimer();

        return Task.CompletedTask;
    }

    public void Dispose()
    {
        _timer?.Dispose();
    }

    private void StopTimer()
    {
        _timer?.Change(Timeout.Infinite, 0);
    }
    private void StartTimer() { _timer.Change(TimeSpan.FromSeconds(_emailConfig.TimerIntervalInSeconds), TimeSpan.FromSeconds(_emailConfig.TimerIntervalInSeconds)); }

    private void DoWork(object state)
    {
        StopTimer();
        _processor.Process();
        StartTimer();
    }
}

Answer 1

如您所想，根本原因是在 IIS 中托管时，由于应用程序池回收，您的主机可能会被关闭。这已在下面指出:

It is important to note that the way you deploy your ASP.NET Core WebHost or .NET Core Host might impact the final solution. For instance, if you deploy your WebHost on IIS or a regular Azure App Service, your host can be shut down because of app pool recycles.

Deployment considerations and takeaways

对于可能的解决方法，您可以尝试将空闲超时设置为零以禁用默认回收。

由于 IIS 默认回收，您可以考虑不同的托管方法:

使用 Windows 服务

使用 Docker 容器(Windows 容器)，但为此，您需要 Windows Server 2016 或更高版本。

使用 Azure 函数

对于您的情况，您可以尝试 Host ASP.NET Core in a Windows Service